The present invention relates to methods of mounting and demounting upper and lower dies to and from press molding machines and, more particularly, to a method of mounting and demounting upper and lower dies, which is suitably used in a press molding machine of transfer type
Generally, when a pair of upper and lower dies of a press molding machine are replaced by other ones, mounting and demounting of the upper and lower dies are done as follows. That is, after pressing has been completed, the upper die is moved upwardly with respect to the lower die to remove a workpiece after having been molded. Subsequently, clamping of the upper die is released
When the clamping of the upper die is released under the condition described above, however, the upper die tends to fall down toward the lower die. Thus, it is required to hold or retain the upper die in any manners.
In view of the above, conventionally, the following method is taken. That is, as shown, for example, in FIG. 2 of the attached drawings, after molding operation has been completed to remove a workpiece from the press molding machine, a storage post 4 is mounted to an outer periphery of a guide post 3 which is mounted to an upper die 1 in an integral manner and which is slidably in a lower die 2 for sliding movement relative thereto. Both upper and lower ends of the storage post 4 are engaged respectively with the upper and lower dies 1 and 2. By doing so, the positional relationship between the upper and lower dies 1 and 2 can be retained.
As shown in FIG. 3, the storage post 4 is constructed as follows. That is, the storage post 4 is formed generally into a cylindrical shape, and has a peripheral wall whose part is formed therein with a cut-out 4a. The guide post 3 is inserted with respect to the storage post 4 through the cut-out 4a. The storage post 4 is formed, at its upper and lower ends, with engaging steps 4b and 4b with which parts of the respective upper and lower dies 1 and 2 are engaged respectively.
However, the following problems still remain even by the conventional method described previously.
Specifically, when the upper and lower dies 1 and 2 are replaced by other ones, it is required to mount and demount the storage post 4 to and from the guide post 3. This increases working steps. Further, since the storage post 4 is separate from the press molding machine, the operation by the use of the separate storage post 4 becomes complicated and troublesome. Moreover, in the case where the storage post 4 is broken due to setting mistake in pre-slide position at a program of the upper and lower dies, or due to the other reasons, other mold parts or components are reduced in accuracy.
Furthermore, since it is impossible for the storage post 4 to bring both the upper and lower dies 1 and 2 to a completely fixed condition, continuous operation of the press molding machine is impossible immediately after the upper and lower dies 1 and 2 have been set, and single processing is required of the order of ten (10) times. Thus, this causes prolongation of the replacement operation of the upper and lower dies 1 and 2.